1. Field of the Invention
The present invention relates to an image projection device and a method of controlling the image projection device.
2. Description of the Related Art
Image projection devices are known that modulate a beam emitted from a light source by using image data from, for example, a personal computer or a camera, and emit the modulated beam onto, for example, a screen to display an image.
For light sources of image projection devices, halogen lamps, metal halide lamps, and high pressure mercury lamps, etc. are used. The temperature of such light sources rises to a maximum of approximately 1000° C. An image projection device takes in air with a blowing unit, such as a blower or fan, from outside the image projection device and circulates the air through the image projection device to cool down the inside of the image projection device. Because the light source in particular rises to a high temperature from among the components in the image projection device, a centrifugal fan may be additionally provided to send the air circulating through the casing to the light source.
A centrifugal fan has a larger number of blades for sending the air than that of an axial flow fan and thus has a small blade pitch, which leads to a narrow flow path. For this reason, dust tends to become attached to centrifugal fans, which tends to lower their blowing ability.
However, conventional-method centrifugal fans for sending the air circulating through the casing to the light source cannot detect the lowering of the blowing ability. There are conventional methods of detecting an abnormality, such as a case where the cooling ability becomes extremely low due to the rotation of a centrifugal fan stopping or a case where a temperature protector is tripped, i.e., because safety cannot be ensured. However, with such abnormality detection methods, lowering of the blowing ability of a centrifugal fan cannot be detected.
Furthermore, a method is known of detecting the clogging of a dust filter by measuring the difference in temperature between the inside and outside of the image projection device (see Laid-open Patent Publication No. 2012-32583). However, even if the difference in temperature between the inside and outside of the image projection device is measured, it cannot be determined whether a problem has occurred in the centrifugal fan.
Therefore, it is desirable to provide an image projection device and a method of controlling the image projection device, each of which can monitor lowering of the blowing ability of the blower for sending the air circulating through the casing to the light source.